| AVS 64th International Symposium & Exhibition | |
| Vacuum Technology Division | Wednesday Sessions |
| Session VT-WeM |
| Session: | Transfer and Ultraclean Systems, Particle Control, and History |
| Presenter: | Hugo Celio, University of Texas at Austin |
| Authors: | H. Celio, University of Texas at Austin K.B. Ohlinger, University of Texas at Austin |
| Correspondent: | Click to Email |
The performance of lithium ion-batteries is steadily improving but there is still need for higher energy density and cycle life in consumer applications. An ex situ investigation of the composition is crucial for investigating performance issues. After a cycling period, the cathode (or anode) material is extracted from a battery coin cell under an argon environment of a glove box. However, a glove box also contains traces of O2 and H2O in the 1-part-per-million range, an unknown amount of adventitious hydrocarbons and inorganic impurities. These traces of oxidants and contaminants are carried along as battery materials are transferred from a glove box to a UHV chamber for surface analysis.
An interface designed to transfer air sensitive materials from a glove box to an ultra-high vacuum (UHV) chamber for surface analysis was previously presented[1]. This interface is called an interface for pressure-to-vacuum environmental sample transfer, or IP-VEST. It is coupled to a UHV chamber equipped with X-ray photoelectron spectroscopy (XPS). The IP-VEST has a built-in method for transfer reliability. However, there is no known method to monitor the degree of oxidation to air sensitive materials from exposure to trace levels of oxidants in argon.
We selected silicon, silver, tin and lithium as a set of reference materials to monitor their surface oxidation and contamination from exposure to trace levels of oxidants, organic, and inorganic contaminants during the environmental transfer of air sensitive battery materials as described above. The preparation procedure for the reference materials is a simple mechanical step which is carried out in the glove box. We focused on evaluating the oxidation rates of clean Si, Ag, Sn and Li with respect to travel time, which is dictated by distance between the glove box and the IP-VEST/UHV chamber. At UT, five glove boxes are located within short distances of each other, entailing a preparation and travel time of less than 30 minutes. Upon arrival to the UHV chamber, the capsule, containing the air sensitive battery materials and reference materials, is coupled to the load-lock of the IP-VEST. This transfer process requires 1 hr. for samples from atmospheric argon pressure to high vacuum conditions. Based on XPS data, the surface oxidation of the reference materials significantly varies but yield a range of oxidation rates. These oxidation rates can be compared to the oxidation rates of some battery materials. The environment of the glove boxes is effectively inert for most cathode materials but insufficient for highly reactive battery materials like lithium.
[1] AVS 2015 and U.S. Patent Application Serial No. 14/445,650